High magnetic moment Co-Fe-O-N films with soft magnetic properties

ABSTRACT

A write element includes a first pole pedestal and a second pole pedestal opposing the first pole pedestal and defining a write gap between the first and second pole pedestals. A first layer of CoFeON is film positioned between the first pole pedestal and the write gap. A second layer of CoFeON film is positioned between the second pole pedestal and the write gap.

FIELD OF THE INVENTION

The present invention relates to a high moment CoFe based film for apole piece layer in a magnetic head, and more particularly, thisinvention relates to the manufacturing and application of high momentCoFeON film for a pole piece layer in a magnetic head.

BACKGROUND OF THE INVENTION

In a disk drive, a magnetic recording head is made of read and writeelements. The write element is used to record and erase data bitsarranged in circular tracks on the disk while the read element playsback a recorded magnetic signal. The magnetic recording head is mountedon a slider which is connected to a suspension arm, the suspension armurging the slider toward a magnetic storage disk. When the disk isrotated the slider flies above the surface of the disk on a cushion ofair which is generated by the rotating disk.

Write heads for disk or tape drives commonly include Permalloy(approximately 80% Ni and 20% Fe), which is formed in thin layers tocreate magnetic features. For example, an inductive head may haveconductive coils that induce a magnetic flux in an adjacent Permalloycore, that flux employed to magnetize a portion or bit of an adjacentmedia. That same inductive head may read signals from the media bybringing the core near the magnetized media portion so that the fluxfrom the media portion induces a flux in the core, the changing flux inthe core inducing an electric current in the coils. Alternatively,instead of inductively sensing media fields, magnetoresistive (MR)sensors or merged heads that include MR sensors may use thinner layersof Permalloy to read signals, by sensing a change in electricalresistance of the MR sensor that is caused by the magnetic signal.

In order to store more information in smaller spaces, transducerelements have decreased in size for many years. One difficulty with thisdeceased size is that the amount of flux that needs to be transmittedmay saturate elements such as magnetic pole layers, which becomesparticularly troublesome when ends of the pole layers closest to themedia, commonly termed poletips, are saturated. Magnetic saturation inthis case limits the amount of flux that is transmitted through thepoletips, limiting writing or reading of signals. Moreover, suchsaturation may blur that writing or reading, as the flux may be evenlydispersed over an entire poletip instead of being focused in a cornerthat has relatively high flux density. For these reasons the use of highmagnetic moment materials in magnetic core elements has been known formany years to be desirable.

In order to write to higher coercivity media, which is more stable oncewritten to, materials with higher magnetization are required to producethe necessary higher flux density. High magnetic moment materials allowapplication of higher flux density or higher field into the media, andthus enable writing to media having higher coercivity. High magneticmoment materials also allow the head to write a smaller bit, i.e., towrite a higher bit density per length of track.

Iron is known to have a higher magnetic moment than nickel, soincreasing the proportion of iron compared to nickel generally yields ahigher moment alloy. Iron, however, is also more corrosive than nickel,which imposes a limit to the concentration of iron that is feasible.Also, it is difficult to achieve soft magnetic properties for iron-richNiFe compared to nickel-rich NiFe. Nitrogen or nickel can be added toNiFe to reduce the magnetic hardness of the film, but the addition ofthese elements can dilute the magnetic moment significantly.

NiFe (80/20 Permalloy) is known to have a magnetization of 10 kGauss.CoFe alloys are known to a have a much higher magnetic moment, with amagnetization of about 24 kGauss. However, CoFe has only recently gainedpopularity as a construction material because it is magnetically hard,i.e., has a high coercivity so it requires a high magnetic field toswitch direction. CoFe is also prone to corrosion.

What is needed is a CoFe based film which takes advantage of the highmagnetization properties of CoFe, but which is also magnetically softand therefore does not need a high current through the coils to switchthe writer.

What is further needed is a CoFe based film which resists corrosion.

SUMMARY OF THE INVENTION

High moment magnetic thin films are important in the manufacture of highdensity magnetic recording devices, specifically in the fabrication ofthe writer. Higher flux densities generated from ever-shrinking writerpoles are required to write data into higher coercivity media.Reactively sputtered Co—Fe—O—N (hereinafter CoFeON) films describedherein have the high magnetic moment required, and additionally are softenough magnetically to function as writer pole materials. Further, theseCoFeON films are resistant to corrosion.

Accordingly, a write element of a magnetic head is provided. The writeelement includes a first pole pedestal and a second pole pedestalopposing the first pole pedestal and defining a write gap between thefirst and second pole pedestals. A first layer of CoFeON is filmpositioned between the first pole pedestal and the write gap. A secondlayer of CoFeON film is positioned between the second pole pedestal andthe write gap.

The layers of CoFeON film preferably contain between 0.2 and 1.0 atomicpercent of N, and ideally between 0.3 and 0.6 atomic percent of N. Thelayers of CoFeON film also preferably contain between 0.2 and 5 atomicpercent of O, and ideally between 0.3 and 1.2 atomic percent of O. Alsopreferably, the layers of CoFeON film contain between 20 and 50 atomicpercent of Co.

Preferred dimensions for the first layer of CoFeON film is between 2000and 4000 Å thick as measured between the first pole pedestal and thewrite gap. Preferred dimensions for the second layer of CoFeON film isbetween 1000 and 2200 Å thick as measured between the second polepedestal and the write gap.

Preferably, the first layer of CoFeON film is longer than the first polepedestal in a direction perpendicular to an air bearing surface of themagnetic head.

The layers of CoFeON film are preferably created during fabrication ofthe magnetic head by sputtering.

Also described is a process for creating a write element of a magnetichead. In the process, a first pole pedestal is added to a first seedlayer such as by plating or deposition. A cap layer of CoFe is added onthe first pole pedestal such as by plating or deposition. The cap layeris sputtered for adding N and O to the cap layer. A write gap layer isadded on the cap layer. A second seed layer of CoFe is added on thewrite gap layer. The second seed layer is sputtered for adding N and Oto the second seed layer. Finally, a second pole pedestal is added onthe second seed layer. Note that other layers may be interspersedbetween those set forth here.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of the presentinvention, as well as the preferred mode of use, reference should bemade to the following detailed description read in conjunction with theaccompanying drawings.

FIG. 1 is a perspective drawing of a magnetic disk drive system inaccordance with one embodiment.

FIG. 2 is a cross sectional view of a magnetic recording head withimproved magnetic characteristics, according to one embodiment.

FIG. 3 is a detailed view taken from circle 3 of FIG. 2 according to apreferred embodiment.

FIG. 4 is a table setting forth results of sputtering under variousoperating conditions.

BEST MODE FOR CARRYING OUT THE INVENTION

The following description is the best embodiment presently contemplatedfor carrying out the present invention. This description is made for thepurpose of illustrating the general principles of the present inventionand is not meant to limit the inventive concepts claimed herein.

Referring now to FIG. 1, there is shown a disk drive 100 embodying thepresent invention. As shown in FIG. 1, at least one rotatable magneticdisk 112 is supported on a spindle 114 and rotated by a disk drive motor118. The magnetic recording media on each disk is in the form of anannular pattern of concentric data tracks (not shown) on disk 112.

At least one slider 113 is positioned on the disk 112, each slider 113supporting one or more magnetic read/write heads 121. More informationregarding such heads 121 will be set forth hereinafter during referenceto FIG. 4. As the disks rotate, slider 113 is moved radially in and outover disk surface 122 so that heads 121 may access different tracks ofthe disk where desired data are recorded. Each slider 113 is attached toan actuator arm 119 by means way of a suspension 115. The suspension 115provides a slight spring force which biases slider 113 against the disksurface 122. Each actuator arm 119 is attached to an actuator means 127.The actuator means 127 as shown in FIG. 1 may be a voice coil motor(VCM). The VCM comprises a coil movable within a fixed magnetic field,the direction and speed of the coil movements being controlled by themotor current signals supplied by controller 129.

During operation of the disk storage system, the rotation of disk 112generates an air bearing between slider 113 and disk surface 122 whichexerts an upward force or lift on the slider. The air bearing thuscounter-balances the slight spring force of suspension 115 and supportsslider 113 off and slightly above the disk surface by a small,substantially constant spacing during normal operation.

The various components of the disk storage system are controlled inoperation by control signals generated by control unit 129, such asaccess control signals and internal clock signals. Typically, controlunit 129 comprises logic control circuits, storage means and amicroprocessor. The control unit 129 generates control signals tocontrol various system operations such as drive motor control signals online 123 and head position and seek control signals on line 128. Thecontrol signals on line 128 provide the desired current profiles tooptimally move and position slider 113 to the desired data track on disk112. Read and write signals are communicated to and from read/writeheads 121 by way of recording channel 125.

The above description of a typical magnetic disk storage system, and theaccompanying illustration of FIG. 1 are for representation purposesonly. It should be apparent that disk storage systems may contain alarge number of disks and actuators, and each actuator may support anumber of sliders.

FIG. 2 is a cross sectional view of a magnetic recording head 200 withimproved magnetic characteristics, according to one embodiment (notdrawn to scale). In FIG. 2, the reference numeral 204 denotes asubstrate, 202 denotes an undercoating, 206 denotes a lower shield layerof the MR/GMR reproducing head part (read element), 208 denotes an uppershield layer of the, 210 denotes a MR/GMR layer provided through aninsulating layer 212 between the lower shield layer 206 and the uppershield layer 208, 213 denotes a bottom writer pole of the write element,214 denotes a pedestal on the bottom writer pole, 216 denotes top writepole tip above a write gap 215, 218 denotes a first coil layer, 219denotes a second coil, 220 denotes an upper insulating layer depositedso as to cover the second coil conductor 219, and 222 denotes an upperpole stitched to the top pole tip 216 near the ABS. The upper pole 222is magnetically connected with the bottom pole (upper shield layer) 208at its rear portion so as to constitute a magnetic yoke together withthe lower pole 208.

Referring to FIG. 2, a pad 226 is operatively coupled to a layer 228positioned between the pad 226 and the undercoating 202, or can bepositioned directly on the undercoating 202. For example, electriccontact pads of the read and write elements are preferably separatedfrom the undercoating by insulation planarization layers 228. Layer bylayer planarization is preferably used, so the pad 226 can be addedlater, at a position away from the undercoating 202. Accordingly, one ormore planarization layers 228 of Al₂O₃ are deposited on top of andbeside the lower shield layer 206 and planarized back to the lowershield layer 206. Additional layers can be added.

As will be appreciated by one skilled in the art, additional layers andcomponents not described herein may also be added. Also, not all layersshown are necessary. Finally, conventional materials may be used formost of the layers in addition to or instead of those mentioned herein.

High moment magnetic thin films are important in the manufacture of highdensity magnetic recording devices, specifically in the fabrication ofthe writer. Higher flux densities generated from ever-shrinking writerpoles are required to write data into higher coercivity media.Reactively sputtered CoFeON films described here have the high magneticmoment required and additionally are soft enough magnetically tofunction as writer pole materials.

In developing the high moment CoFe based film, it was found that byusing the correct processing conditions, a small amount of oxygen can beincorporated into the CoFeN film. The resulting CoFeON film was found tohave much lower coercivity than the corresponding CoFe or CoFeN filmwithout oxygen. An optimal amount of oxygen in the film was also foundto not have the detrimental effect of lowering the magnetic moment. Ithas also been demonstrated that the use of this film improves writerperformance significantly.

In experiments performed, the introduction of N into a CoFe film reducedthe coercivity from over 100 to about 15–25 oersted. Magnetization alsodrops upon addition of N from about 24 kGauss to about 23 to 23.5kGauss. Thus, the use of N provides a good balance between the desirablesoft magnetic properties and high magnetization.

N also reduces corrosion in these films, which is desirable because thelife of the head is extended.

The small amount of O added to the film further lowers the coercivity ofthe film and does not significantly lower the magnetization. Experimentshave shown that the addition of O does not detrimentally affect thecorrosivity of the film.

Note that O and N are added to the lattice of the CoFe by sputtering.Compounds are not created, i.e., this is not a nitride- or oxide-metalfilm. Rather the resulting film is a nitrogenated and/or oxygenatedfilm. Nor should the nomenclature of the film, i.e., CoFeON, beconsidered to represent the stoichiometry of the resulting film.

FIG. 3 is a detailed view taken from circle 300 of FIG. 2 according to apreferred embodiment. As shown, a lower pedestal seed layer 302 ispositioned between the lower writer pole 213 and the pedestal 214. A caplayer 304 of CoFeON is positioned between the lower pedestal 214 and thewrite gap 215. As shown, this cap may extend beyond the lower pedestal214 in a direction perpendicular to and away from the air bearingsurface (ABS).

An upper pedestal seed layer 306 of CoFeON is positioned between theupper pedestal 216 and the write gap 215. Preferably, the upper pedestalseed layer 306 does not extend beyond the upper pedestal 216 in adirection perpendicular and away from the ABS. For purposes of thepresent discussion, assume that the pedestals 214,216 are of NiFe.

Each film stack of the CoFeON and NiFe has a low coercivity. This issignificant in that the interaction of the layers 214,304 and/or 306,216make the entire film stack softer. According to one experiment, themagnetization of the stack (214,304 and/or 306,216) was about 23.5kGauss while the magnetization of the NiFe pedestal alone was about 22kGauss.

The strategic positioning of the cap 304 and upper pedestal seed layer306 adjacent the write gap 215 provides the highest magnetization acrossthe write gap 215; that is the highest density field from the writer.

The following simplified description is of an illustrative partialmanufacturing process for generating the portion of the writer elementshown in FIG. 3. Note that exemplary values and materials have beenadded for illustrative purposes only and are not meant to infer limitingvalues, ranges or substances.

To plate the write element, the lower pedestal seed layer 302 is addedto the bottom writer pole 213. The lower pedestal 214 is plated on thelower pedestal seed layer 302. The lower pedestal 214 in an illustrativeembodiment can be about 4 microns of high iron NiFe (22/78). A lowerpedestal cap 304 is added by plating 2000–4000 Å (ideally about 3000 Å)of CoFe onto the lower pedestal 214. O and N are sputtered into thelayer 304 of CoFe. The write gap 215, which can be made of alumina(Al₂O₃), is plated or deposited on the CoFeON film 304.

The upper pedestal seed layer 306 is added, which in this example is1000–2200 Å (ideally about 1600 Å) of CoFeON deposited and sputtered onthe write gap 215. The upper pedestal seed layer 306 is so named becauseit acts as a seed layer upon which about 4 microns of high iron NiFe(22/78) is plated to form the upper pedestal 216. Preferably, the upperpedestal seed layer 306 does not extend beyond the upper pedestal 216 ina direction perpendicular and away from the air bearing surface, and canbe milled to the desired dimensions.

Note that additional layers may be interspersed between those set forthhere.

The layers of CoFeON film preferably contain between 0.2 and 1.0 atomicpercent of N, and ideally between 0.3 and 0.6 atomic percent of N. Thelayers of CoFeON film also preferably contain between 0.2 and 5 atomicpercent of O, and ideally between 0.3 and 1.2 atomic percent of O. Alsopreferably, the layers of CoFeON film contain between 20 and 50 atomicpercent of Co.

As mentioned above, the CoFeON films described herein are created bysputtering. Following is a brief description of a sputtering processthat may be used. Again, values have been added to aid in understandingthe process and are not meant to be limiting.

The sputtering target is a CoFe alloy and is placed in a sputteringchamber. The chamber is evacuated and backfilled with an inert processgas, such as Ar, at a low pressure. N is introduced in the process gasduring the sputtering deposition. In a exemplary embodiment, N is about1% of the background, while O is about 0.01% in the background.

Preferably, N is premixed into the Ar. O can also be premixed into theAr, or can be controlled by allowing small amounts of resident gases toremain in the chamber after evacuation.

An electrical charge is applied to a filament in the chamber to strike aplasma. The result is removal of electrons from the Ar and creation ofAr ions (Ar+ and Ar++). This creates a plasma.

A radio frequency (RF) signal of about 13.56 MHz is applied to thesputtering target to create a bias. The negative bias on the targetaccelerates the Ar ions towards the target to dislodge Co and Fe atomsfrom the target. As mentioned above, O and N are added to the lattice ofthe CoFe film during film growth. Compounds are not created, nor is thefilm a nitride- or oxide-metal film. Rather the resulting film is anitrogenated and/or oxygenated film.

The amount of O can be controlled by sputtering Ta onto collateralobjects in the sputtering machine, such as shielding in the sputteringchamber. Ta acts as a getter of O, rendering the O inactive in thesystem.

The addition of N in the system enhances the acquisition of O into thefilm.

FIG. 4 is a table 400 setting forth results of sputtering under variousoperating conditions.

Another way to create the film is through use of a DC magnetron.

In use, the recording head structure and improvements set forth hereincan be used in magnetic recording heads for any type of magnetic media,including but not limited to disk media, magnetic tape, etc.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of a preferred embodiment shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

1. A write element of a magnetic head, comprising: a first polepedestal; a second pole pedestal opposing the first pole pedestal anddefining a write gap between the first and second pole pedestals; afirst layer of CoFeON film positioned between the first pole pedestaland the write gap; and a second layer of CoFeON film positioned betweenthe second pole pedestal and the write gap.
 2. The magnetic head asrecited in claim 1, wherein at least one of the layers of CoFeON filmcontains between 0.2 and 1.0 atomic percent of N.
 3. The magnetic headas recited in claim 2, wherein at least one of the layers of CoFeON filmcontains between 0.3 and 0.6 atomic percent of N.
 4. The magnetic headas recited in claim 1, wherein at least one of the layers of CoFeON filmcontains between 0.2 and 5 atomic percent of O.
 5. The magnetic head asrecited in claim 4, wherein at least one of the layers of CoFeON filmcontains between 0.2 and 1.2 atomic percent of O.
 6. The magnetic headas recited in claim 1, wherein at least one of the layers of CoFeON filmcontains between 20 and 50 atomic percent of Co.
 7. The magnetic head asrecited in claim 1, wherein the first layer of CoFeON film is between2000 and 4000 Å thick as measured between the first pole pedestal andthe write gap.
 8. The magnetic head as recited in claim 1, wherein thesecond layer of CoFeON film is between 1000 and 2.200 Å thick asmeasured between the second pole pedestal and the write gap.
 9. A writeelement of a magnetic head, comprising: a first pole pedestal; a secondpole pedestal opposing the first pole pedestal and defining a write gapbetween the first and second pole pedestals; a first layer of CoFeONfilm positioned between the first pole pedestal and the write gap; and asecond layer of CoFeON film positioned between the second pole pedestaland the write gap; wherein the first layer of CoFeON film is longer thanthe first pole pedestal in a direction perpendicular to an air bearingsurface of the magnetic head.
 10. The magnetic head as recited in claim1, wherein the first and second layers of CoFeON film are created duringfabrication of the magnetic head by sputtering.
 11. A write element of amagnetic head, comprising: a write gap; a pole pedestal; and a layer ofCoFeON film positioned along one side of the write gap between the polepedestal and the write gap.
 12. The magnetic head as recited in claim11, wherein the layer of CoFeON film contains between 0.2 and 1.0 atomicpercent of N.
 13. The magnetic head as recited in claim 12, wherein thelayer of CoFeON film contains between 0.3 and 06 atomic percent of N.14. The magnetic head as recited in claim 11, wherein the layer ofCoFeON film contains between 0.2 and 5 atomic percent of O.
 15. Themagnetic head as recited in claim 14, wherein the layer of CoFeON filmcontains between 0.3 and 1.2 atomic percent of O.
 16. The magnetic headas recited in claim 11, wherein the layer of CoFeON film containsbetween 20 and 50 atomic percent of Co.
 17. A write element of amagnetic head, comprising: a write gap; and a layer of CoFeON filmpositioned along one side of the write gap; wherein the layer of CoFeONfilm is longer than an adjacent pole pedestal in a directionperpendicular to an air beating surface of the magnetic head.
 18. Themagnetic head as recited in claim 11, wherein the layer of CoFeON filmis created during fabrication of the magnetic head by sputtering.
 19. Awrite element of a magnetic head, comprising: a first pole pedestal. asecond pole pedestal opposing the first pole pedestal and defining awrite gap between the first and second pole pedestals; and a layer ofCoFeON film positioned between at least one of the pole pedestals andthe write gap.
 20. The magnetic head as recited in claim 19, wherein thelayer of CoFeON film contains between 0.2 and 1.0 atomic percent of N.21. The magnetic head as recited in claim 19, wherein the layer ofCoFeON film contains between 0.2. and 5 atomic percent of O.
 22. Amagnetic storage system, comprising: magnetic media; at least one headfor reading from and writing to the magnetic media, each head having; asubstrate; a read element coupled to the undercoating; and a writeelement coupled to the read element, the write element comprising; afirst pole pedestal; a second pole pedestal opposing the first polepedestal and defining a write gap between the first and second polepedestals; and a layer of CoFeON film positioned between at least one ofthe pole pedestals and the write gap a slider for supporting the head;and a control unit coupled to the head for controlling operation of thehead.